226 



INTESTINAL DIGESTION 



slightly, to where the sigmoid flexure opens into the rectum. This is 

 the narrowest portion of the canal. Beyond this, the rectum gradually 

 increases in diameter, forming a kind of pouch, which abruptly dimin- 

 ishes in size near the external opening, to form the anus. 



The general direction 

 of the large intestine is 

 from the caecum, in the 

 right iliac fossa, to the 



i ii : 'ii ^i BRF ~- ; ^iiMur ^" ^ ac f ssa tnus en ~ 



circling the convoluted 

 small intestine, in the 

 form of a horseshoe. 

 From the caecum to the 

 rectum, the canal is 

 known as the colon. 

 The first division of the 

 colon, called the ascend- 

 ing colon, passes almost 

 directly upward to the 

 under surface of the 

 liver; the canal here 

 turns at nearly a right 

 angle, passes across the 

 upper part of the abdo- 

 men and is called the 

 transverse colon ; it then 

 passes downward at 

 nearly a right angle, 

 forming the descending 

 colon. The last division 

 of the colon, called the 

 sigmoid flexure, is situ- 

 ated in the left iliac fossa 

 and is in the form of the 

 italic letter 5. This ter- 

 minates in the rectum, 

 which is not straight, 



as its name would imply, but presents at least three distinct curvatures, 

 as follows : it passes first in an oblique direction from the left sacro-iliac 

 symphysis to the median line opposite the third piece of the sacrum ; 

 it then passes downward in the median line, following the concavity 

 of the sacrum and coccyx ; and the lower portion, which is about an 



Fig. 48. Stomach, pancreas and large intestine (Sappey). 



I, anterior surface of the liver; 2, gall-bladder; 3, 3, section 

 of the diaphragm ; 4, posterior surface of the stomach ; 5, lobus 

 Spigelii of the liver ; 6, coeliac axis ; 7, coronary artery of the 

 stomach; 8, splenic artery; 9, spleen; 10, pancreas; n, supe- 

 rior mesenteric vessels ; 12, duodenum ; 13, upper extremity of 

 the small intestine ; 14, lower end of the ileum ; 15, 15, mesentery ; 

 16, ccecum ; 17, appendix vermiformis ; 18, ascending colon ; 19, 

 19, transverse colon ; 20, descending colon ; 21, sigmoid flexure of 

 the colon ; 22, rectum ; 23, urinary bladder. 





